[Blindmath] A 3d to 2d description resource?

[Michael Whapples]

Regarding the thing about the cylinder looking like a rectangle from the 
side. Try thinking of it by imagining viewing it from the side, what are the 
most extreme points of what would be visible? What shape do these create? A 
valid question might be, but why doesn't the bit coming towards me alter 
things? I have two answers to this. Firstly the simple one is to think of it 
as Richard described about how people see in 2D, when using two eyes you get 
an image from two slightly different angles and a clever bit of processing 
can say what 3D shape would create the difference between the two images. If 
you only have a single detector (eg. a single camera with a single lens) 
then the bulge in the cylinder cannot be detected as the distance cannot be 
identified. The more complicated answer, well some drawings you may 
encounter may show one side of the rectangle (representing the side of the 
cylinder) with one side darker than the other, this probably is to show 
where the shadow is forming if the light were coming from one side. If light 
were coming from all directions then no such shading should be drawn as no 
shadow would form.

Michael Whapples

-----Original Message----- 
From: Pranav Lal
Sent: Tuesday, January 31, 2012 4:08 PM
To: john.gardner at orst.edu ; 'Blind Math list for those interested in 
mathematics'
Subject: Re: [Blindmath] A 3d to 2d description resource?

Hi John,
<snip
If anybody would like to organize an archive of images and tutorials that
could explain the principles of 3d to 2d projections understandable by blind
people, it would be a good subject for the www.Access2Science.com web site.
PL] I would be happy to do this. I was thinking about a wiki where we could
start adding descriptions and linking to relevant SVG files.

<snip This seems to be one of the most difficult
things for most congenitively blind people to understand.  As a person who
was sighted for much of my life, I understand it intuitively but have never
tried to explain it to someone who didn't understand it.  The idea of
projection should not be too difficult.  But projection is only a tiny part
of drawing images.
PL] I am congenitively blind so can relate to this. I was discussing this
with my civil engineer dad and he mentioned that a cylindrical glass would
look like a rectangle when seen in 2d. This is totally beyond me right now.
Engineers learn all this in a subject called engineering drawing. Has anyone
on this list studied it?

Pranav


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